This invention relates to an indicator element comprising a light permeable cap in which a light source is at least partially disposed, and a protective sleeve in the interior of which connecting conductors for the light source are arranged.
A indicator element of this type is disclosed in Uchida, U.S. Pat. No. 4,727,289, which contains light emitting diodes (LEDs) as the light source. The LEDs are disposed on a printed circuit and are located inside a light permeable cap which takes the form of a glass bulb joined to a base of metal. This base serves as a protective sleeve for the electrical conductor disposed inside of it and as a holder for mounting the printed circuit board on stays. A resistor is furthermore disposed in the interior of the base so as to permit direct connection to the line voltage, such as for example 100 volts. The outside dimensions correspond to those of a conventional incandescent lamp with a glass bulb, and miniaturization is not easily possible.
Savage, U.S. Pat. No. 3,887,803 discloses an arrangement with a light emitting diode which is disposed in a cap. The rear end of the cap is engaged in a cylindrical part of a protective sleeve and is joined to the sleeve by snap connections. The connecting conductor as well as a resistor for the LED is disposed in the protective sleeve. Special manufacturing and assembling measures are necessary for fastening the LED to the sleeve. The cap is joined only by a snap connection to the expanded front part of the sleeve and can be pulled forward out of the sleeve, so that in practice damage or even destruction of the LED is always possible.
Indicator elements with incandescent lamps, glow discharge lamps and light emitting diodes may have an all-plastic body, or also a threaded metal base, for mounting in a switchboard, panel or the like. Furthermore, such indicator elements contain insulators and contacts for electrical connection. Due to their physical construction, small indicator elements with incandescent lamps and light emitting diodes cannot be operated directly on line voltages of 110 to 250 volts AC so as to provide enough brightness to reliably indicate the states of "on" and "off." A reliable signal function can be achieved up to a voltage of 60 volts AC or DC. This does not apply to indicator elements with glow discharge lamps which because of their particular characteristics are used for the above-mentioned line voltages.